Gunmen have seriously wounded 73-year-old conservationist Kuki Gallmann at her conservation park in the latest of a string of attacks during land invasions in drought-stricken northern Kenya.

The Italian-born author of the memoir I Dreamed of Africa was shot in the stomach on Sunday after the vehicle she was driving in was ambushed, a family friend said.

Gallmann was going to inspect damage to her property after invaders burned down a retreat there on Saturday. A luxury hotel had already been torched last month.

Kenya declares national disaster after severe drought

She was ambushed when she was forced to stop by a tree laid across the road, the friend said.

The gunmen shot her, but Gallmann was saved when rangers from the Kenya Wildlife Service intervened and fought off the attackers.

Gallmann was flown by helicopter to receive surgery at a hospital in Kenya's capital, Nairobi.

Her daughter - who herself was shot at in an incident in March - said her mother was able to speak, the friend said.

The Gallmann family own the 400 square km Laikipia Nature Conservancy and employ 250 Kenyans on the luxury lodges, ranch, and other businesses on the land.

They also run the Gallmann Africa Conservancy and Gallmann Memorial Foundation, conservation groups focusing on bringing people and wildlife together sustainably.

'Unable or unwilling to stop'

A wave of violence has hit Kenya's drought-stricken Laikipia region in recent months as armed cattle-herders searching for scarce grazing land have driven tens of thousands of cattle on to private farms and ranches from poor quality communal land.

Many residents of the area accuse local politicians of inciting the violence before the August elections.

They say that the politicians are trying to drive out voters who might oppose them and win votes by promising supporters access to private land.

Martin Evans, head of the Laikipia Farmers' Association, condemned the attack on Gallmann and said "dozens of people have been killed or wounded and subjected to robbery and vandalism of their property. Kuki is a world-famous author and conservationist - but the LFA urges sympathy for all".

Raila Odinga, the country's veteran opposition leader, condemned the attack and said "we have watched in bewilderment as hooligans take advantage of the drought to subject these ranchers to unwarranted attacks... The government is clearly unable or unwilling to bring these attacks to a stop".

National police spokesman George Kinoti said a local politician was already facing charges for inciting violence and arson attacks in the area.

"We also wish to caution certain politicians to refrain from making statements that amount to encouraging ranch invasion," he said in a statement.

At least 14 civilians have been killed, including local resident Duncan Murimi who was shot in the stomach and who died three days ago on a neighbouring property. Another Kenyan man was killed a few days before him in the same area.

Four police have been killed in the last six weeks, Kenyan media reported. Police spokesmen did not return calls seeking comment.

Last month, Tristan Voorspuy, a British military veteran who ran a safari company in Kenya, was shot dead at a private ranch in Laikipia.

He had gone to the ranch to inspect the remains of a friend's home that had been burned down.